Reginar was
lay abbot of important abbeys stretching from the
Meuse () to the
Moselle through the
Ardennes, Saint-Servais in
Maastricht, Echternach,
Stavelot-Malmedy, and Saint-Maximin in
Trier. All these abbeys lay on or near the boundary negotiated between the Eastern and Western Frankish kingdoms in the
Treaty of Meerssen in 870, during a period when the Western Kingdom controlled much of Lotharingia. In Echternach, he was referred to as "Rainerus iunior" because the lay abbot before him, a probable relative, had the same name. Reginar's secular titles and activities are mainly only known from much later sources which are considered to be of uncertain reliability.
Dudo of Saint-Quentin, in describing the great deeds of the early
Normans, calls Reginar I (who, along with a prince of the
Frisians named Radbod, was an opponent of
Rollo, the founder of Normandy) a duke of both Hainaut and Hesbaye. Centuries later
William of Jumièges, and then later still,
Alberic de Trois Fontaines followed Dudo using the same titles when describing the same events. He was variously referred to as duke, count, marquis,
missus dominicus, but historians doubt that these titles were connected to a particular territory. That he called himself a duke is known from a charter at Stavelot 21 July 905, but this was during a period when
Gebhard was duke of Lotharingia. Reginar was originally a supporter of
Zwentibold (King of Lotharingia) in 895, but he broke with the king in 898. He and some other magnates who had been key to Zwentibold's election three years earlier then took the opportunity provided by the death of
Odo of France to invite
Charles the Simple to become king in Lotharingia. His lands were confiscated, but he refused to give them up and entrenched himself at
Durfost, downstream from Maastricht. Representatives of Charles, Zwentibold, and the
Emperor Arnulf met at
Sankt Goar and determined that the succession should go to
Louis the Child. Zwentibold was killed by Reginar in battle in August 900. Louis appointed
Gebhard as his duke in Lotharingia. In 908, Reginar recuperated Hainaut after the death of
Sigard. Then, after the death of Gebhard in 910, in battle with the
Magyars, Reginar led the magnates in opposing
Conrad I of Germany and electing Charles the Simple as their king. He never appears as the duke of Lorraine, but he was probably the military commander of the region under Charles. He was succeeded by his son
Gilbert; however, the Reginarids did not succeed in establishing their supremacy in Lotharingia like the
Liudolfings or
Liutpoldings did in the duchies of
Saxony and
Bavaria. ==Family==